Duct assembly system

ABSTRACT

The present invention is embodied in a duct assembly system for the shaping and support of skins against a bulkhead, including an articulating skin expanding member conforming, in an extended position, to a cross section of the bulkhead, and a support means attached to the expanding member for insertion of the expanding member into the skins and alignment of the expanding member adjacent to the bulkhead.

BACKGROUND OF THE INVENTION TECHNICAL FIELD

The present invention relates to a duct assembly system for the shapingand support of structural components, such as skins, to a bulkhead forthe purpose of fastening the component to the bulkhead.

BACKGROUND ART

In the manufacture of jet aircraft, the assembly of the engine intakeducts to the aircraft bulkheads has posed a major assembly problem thathas been previously overcome by numerous manual assembly steps. Thesesteps have not only been costly and time consuming, but they have alsorequired difficult physical manipulation steps by assemblers.

The ducts are comprised of curved sections of metal or composite sheetsknown as "skins". The skins are to be inserted into the aircraftbulkheads and held in place using various conventional support devices,such as c-clamps or temporary interlocking fasteners that attach to eachbulkhead, known as "clickos". These manual positioning methods presentseveral disadvantages. Initially, the manual insertion of the skins intothe bulkhead structure requires extensive physical lifting, bending andsupporting maneuvers by assembly personnel until the support devices areattached. In addition, the pressure exerted by the support devices, suchas clickos, against the bulkheads varies and can cause the skins to warpand bend.

These manual assembly tools also cause difficulties for assemblypersonnel because of the manner in which the skins must be fastened tothe bulkheads. The skins must be attached to the bulkheads by insertingfasteners from the interior side of the skin into the bulkhead becausethe interior of the duct must remain smooth to maintain the laminar flowof intake air and because there is no access from the bulkhead side ofthe ducts to insert the fasteners. Thus, personnel must be inside theduct while drilling fasteners into the bulkheads. Unfortunately, theassembly tools described earlier, such as c-clamps and clickos, extendinto the duct interior and substantially interfere with the movement ofassembly personnel while they are inside the duct fastening the skins tothe bulkheads.

These problems are compounded if the skins are made of compositematerials, such as a graphite epoxy, because a liquid shim, such as anepoxy resin, must be used between the skin and bulkhead to assure apermanent bond. In order to cure this shim, a uniform pressure isrequired to be applied over the surface between the bulkhead and skinduring a cure period, which can be approximately 24 hours. It isdifficult for the conventional support devices described earlier toachieve such a uniform pressure and to maintain it over such a long cureperiod.

The need to achieve and maintain a uniform outward pressure over thecontact surface between the bulkhead and skin is complicated by the factthat the cross sections of a duct frequently vary within a duct from acircular shape to other arcuate shapes. Using the conventional clampingdevices, many more devices are needed to achieve uniform outwardpressure at each cross section in ducts that have varying crosssections, as compared to a duct with uniformly circular cross sections.

SUMMARY OF THE INVENTION

The present invention is embodied in a duct assembly system for theshaping and support of skins against a bulkhead, including anarticulating skin expanding member conforming, in an expanded position,to a cross section of the bulkhead, a support means attached to theexpanding member for insertion of the expanding member into the skinsand alignment of the expanding member adjacent to the bulkhead, and apower source to extend the expanding member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a system of the present invention in acollapsed position being inserted into a bulkhead structure.

FIG. 2 is a perspective view of the system of FIG. 1 in an expandedposition.

FIG. 3 is a partial cross sectional view along the line 3--3 of FIG. 2

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

As shown in FIG. 1, the duct assembly system 50 includes articulatingskin expanders 100 that are mounted on support tubes 105 at distancescorresponding to the spacing between bulkheads 110. The expanders 100are segmented by hinges 115, the number of which is determined by theshape of a particular bulkhead 110 against which the expander must bepositioned. For example, in FIG. 1 expander 100a has four expandersegments 125 because the cross section shapes of the bulkheads 110 aregenerally square with rounded corners. In addition, the shape of eachexpander segment 125 depends on the shape of the specific bulkheadagainst which it is positioned. For example, in FIG. 1, the expandersegments 125b of expander 100b are more arcuate in shape than expandersegments 125a of expander 100a because the cross section of the duct 120is more curved at bulkhead 110b than bulkhead 110a.

Air cylinders 130 are mounted intermediate each pair of expandersegments 125 that are joined by a hinge 115. The support tubes 105contain air pressure lines (not shown) that transport pressurized air tothe air cylinders 130. Each expander segment 125 contains one or morebladder segments 135 that also receive pressurized air from the airpressure lines in the support tubes 105.

As shown in FIG. 2, one or more heating coils 170 may be mounted in eachexpander segment 125 when a composite material is used to form the duct120. The support tubes 105 contain electrical conducting means (notshown) to carry electric current to the heating coils 170. Observationlights 175 are mounted in tubes 105 or expander segments 125 and alsoreceive electric current from the conducting means in the tubes 105.Removable work platforms 180 are mounted on the tubes 105 by hinges orother suitable attachment means for the support of assembly personnelworking inside the skin expanders 100 after they have been extended byair cylinders 130.

A series of bushings 190 are mounted on each expander segment 125. Thebushings 190 are spaced at positions on the expander segments 125 whereit has been determined suitable for holes to be drilled in the skins andfasteners inserted to secure the skins to the bulkheads 110. Bushings190 may also be fitted with twist interlock adapters 195 for theattachment of automatic drills, for "peck drilling".

The expander segments 125 and tubes 105 are also fitted with air flownozzles 200 that receive air from the air pressure lines in the tubes105 and exhaust the air through the open ends of the duct 120 duringassembly. The expander segments 125 that are mounted under the tubes 105are also fitted with bearings 205, such as air bearings or nylonbearings, to facilitate insertion of the system 50 in the duct 120 priorto extension of the expanders 125.

The support tubes 105 are connected at one end with a control panel 210that contains appropriate control switches for lights 175, cylinders130, coils 170 and nozzles 200. The control panel is also provided withmanipulation means 215, such as handles, to insert the system 50 in theduct 120.

As shown in FIG. 3, a locking air cylinder 220 joins the expandersegments 125 that are not joined by hinges 115 (as show in FIG. 1). Alocking pin 225 is extended by cylinder 220 from the expander segment125 containing the cylinder 220 into a locking plate 230 in the expandersegment 125 to be joined.

Prior to operation of the system 50, the skins 121 comprising the duct120 must be temporarily mounted and aligned in the bulkheads 110 bymeans of conventional c-clamps. If the skins 121 are made of compositematerials, a liquid shim such as an epoxy resin is applied to the skins121 along the portion of the skins 121 that will contact the bulkheads.Since the liquid shim begins to cure almost immediately, the system 50is then quickly transported in an unexpanded position as shown in FIG. 1to the duct 120. Any suitable transporting means, such as a collapsiblestand 250, may be used to maneuver the system 50 adjacent the duct 120.

An operator then pushes the system 50 into the duct 120 by using themanipulation means 215, sliding on bearings 205 until the expanders 100are aligned with the bulkheads 110. Pressurized air is then released tothe cylinders 130 by means of an appropriate switch on the control panel210 to expand the expander segments 125 to conform to the cross sectionsof the bulkheads 110. The operator then activates cylinders 220 to lockthe ends of expander segments 125 that are not joined by hinges 115 inorder that the expanders 100 form rigid assemblies.

Bladders 170 are then inflated to apply uniform outward pressure againstthe skins 121 to the bulkheads 110 to shape the skins to the bulkheadand support it during assembly of the skins to the bulkhead. Typically,a pressure of 30 pounds per square inch is used for skins of a thicknessof 0.130 inch. Holes may then be drilled through the skins 121, usingthe bushings 190 as guides, and into the bulkheads 110 for insertion offasteners to complete the assembly operation. If the skins 121 are madeof a composite material and a liquid shim was applied as describedearlier, the heating coils 170 may be activated to accelerate the curingcycle for the liquid shim. This heating reduces the cure period, forexample, from 24 hours to 72 minutes for liquid shim made of epoxyresin. During the curing process, the nozzles 200 are activated toremove any fumes released by the curing process. After the shim hascured, the holes may then be drilled in the skins 121.

Assembly of aircraft engine ducts or other structural components intoframes using the present invention has several significant advantagesover conventional assembly techniques. A major advantage is the savingsin time and cost in completing such operations using the invention. Thetime previously spent in installing and removing the temporary supportdevices, such as clickos, is avoided. In addition, the inconvenience andtime spent by assembly personnel in avoiding such devices while drillingholes in the duct is avoided. The improved assembler access providedinside the duct also reduces assembler fatigue, accidents and results infewer errors in the drilling of holes.

In addition, the invention applies a uniform outward pressure on thecomponents irrespective of the cross section shapes of the frames orbulkheads to which the components are being attached by using expandingsections that conform to each such cross section and pressurizedbladders. This uniform pressure enables more precise placement of holesand skins, which eliminates stress induced deformations at the clampingpoints (i.e. using clickos) caused by the curing process.

If the components are made of composite materials, the invention alsooffers some unique and very specific advantages. Since the inventionapplies a more uniform pressure than conventional methods to the portionof skins to which liquid shim is applied, the strength and uniformity ofthe bond is improved. The invention also applies heat during the curingcycle, which drastically reduces the curing time required to reach fullbond strength and results in a significant cost savings. The inventionalso provides means to evacuate the fumes from the curing process whichenables assemblers to enter the duct sooner for inspection and assemblyoperations.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention.

What is claimed:
 1. A duct assembly system for shaping and supporting askin against a bulkhead to form a duct, comprising:an articulating skinexpanding member conforming, in an expanded position, to a cross sectionof said bulkhead, said expanding member applying uniform pressure on theskin against the bulkhead and comprising a plurality of bushings fordrilling fastener holes in said skin; and support means for insertion ofsaid expanding member into said duct and alignment of saidexpanding,member adjacent to said bulkhead.
 2. The system of claim 1wherein said expanding member comprisesa plurality of hinged skinexpanding segments; and an actuator to expand and collapse saidsegments.
 3. The system of claim 2 wherein said actuator comprisesan aircylinder disposed between adjacent hinged segments.
 4. The system ofclaim 2 wherein said expanding member further comprisesskin expandingsegments having at least two unhinged ends; and locking means to securesaid unhinged ends.
 5. The system of claim 1 wherein said expandingmember further comprisesa skin expanding bladder for exerting pressureon said skin against said bulkhead.
 6. The system of claim 1 whereinsaid expanding member further comprisesheating coils for curing adhesiveapplied to a bulkhead facing surface of said skin.
 7. The system ofclaim 1 further comprisingillumination means affixed to said expandingmembers.
 8. The system of claim 1 further comprisingillumination meansaffixed to said support means.
 9. The system of claim 1 furthercomprisingair introduction nozzles affixed to said expanding members forproviding ventilation; and a source of pressurized air connected to saidnozzles.
 10. The system of claim 1 further comprisingair introductionnozzles affixed to said support means for providing ventilation; and asource of pressurized air connected to said nozzles.
 11. The system ofclaim 1 further comprisinga plurality of said expanding members affixedto said support means at positions corresponding to positions of aplurality of bulkheads to which said duct is assembled.
 12. A ductassembly system for shaping and supporting a skin against a bulkhead,comprising:means for expanding and uniformly applying pressure againstsaid skin against a cross-section of said bulkhead, said expanding meanscomprising a plurality of bushings for drilling fastener holes in saidskin; means to support and align said expanding means adjacent to saidbulkhead; and an actuator to expand said expanding means.
 13. The systemof claim 12 wherein said expanding means compriseshinged collar segmentshaving at least two unhinged ends; and locking means to secure saidunhinged ends.
 14. The system of claim 12 further comprisinga pluralityof said expanding means affixed to said support means at positionscorresponding to positions of a plurality of bulkheads to which saidduct is assembled.